This invention relates to a self-cooling can. In particular, it relates to a can suitable for containing beverage which includes a refrigeration device within and/or attached to the can so that cooling may be initiated at any time and anywhere, remote from a domestic/commercial refrigerator.
The principles of refrigeration are well-established, using refrigerant in an evaporator to extract heat from the refrigeration compartment (or freezer compartment, as applicable) and then releasing heat from the refrigerant by means of a compressor and condenser or, alternatively, in an absorber.
There are a number of problems associated with adapting known refrigerating units for cooling a beverage in a can. Since the can is to be self-cooling, the refrigeration device needs to be contained in or surround the can. A typical beverage can has, for example, a capacity of 330 ml and tooling, filling and handling equipment is adapted for this size of can. It is clear, therefore, that any internal refrigeration device will either necessitate an increase in can size, with associated equipment changes, or a decrease in the volume of beverage which the can holds.
A further problem is the time taken to cool the volume of liquid to a desired drinking temperature. The flow of liquid/vapour through a miniature refrigeration device and the choice of refrigerant may be limiting factors in this. Clearly a non-toxic refrigerant is at least desirable and possibly essential for use with beverage.
Finally, initiation of the cooling process should ideally be a simple procedure for the consumer to carry out.
U.S. Pat. No. 4,669,273 describes a self-cooling beverage container which uses a coiled tube within the beverage can which releases a pressurised refrigerant to an evaporator for cooling the beverage. Not only does this device severely limit the capacity of the can available for the beverage but there is also a safety issue involved in the use of a pressurised refrigerant within the can.
Phase change cooling devices are described in U.S. Pat. No. 4,759,191, U.S. Pat. No. 4,901,535, U.S. Pat. No. 4,949,549, U.S. Pat. No. 4,993,239 and U.S. Pat. No. 5,197,302, for example. Such devices typically have an evaporator chamber and an evacuated absorber chamber. Liquid such as water in the evaporator vaporises due to a drop in pressure when a valve between the two chambers is opened and therefore removes heat from the evaporator to do so. Latent heat of vaporisation is then absorbed by heat removing material in the absorber chamber. U.S. Pat. No. 5,018,368 uses a desiccant/heat sink device for absorbing water vapour from the evaporator.
These phase change materials are generally not preferred for cooling a product with a can due to the loss of can capacity available for the product itself. Furthermore the length of time taken to cool the can of beverage is often unacceptable for practical purposes. There is a general need for improved can cooling devices and methods.
According to the present invention, there is provided a self cooling can comprising: a cylindrical can body for beverage product; an evaporator within the can body for removing heat from beverage product surrounding the evaporator, the evaporator comprising an annular component having an inner and outer wall with a gap between the walls, the curled edge of the outer wall being clipped onto a ridge on the inside chine wall of the base of the can body to form a sealed unit which holds a high vacuum and is isolated from beverage product; an absorber unit fixed to the outside of the can body and including a first desiccant region and a second region containing heat sink material, either the desiccant region or the second region of the absorber unit comprising an absorber element having one or more pockets for the desiccant or heat sink material respectively; and means for providing a vapour path from the evaporator to the absorber unit such that, in use, when the vapour path is opened, vapour passes from the evaporator to the desiccant region of the absorber unit, the vapour being absorbed by the desiccant and heat from the vapour and/or the reaction of the desiccant being removed by the heat sink material, thereby cooling product around the evaporator.
By using an absorber which is external to the can, only the evaporator will reduce the can capacity available for the product.
By separating the absorber from the evaporator, any risk that heat removed by the absorber offsets or even negates the cooling effect of the evaporator is avoided. The use of an evaporator and external absorber unit means that the product is entirely isolated from the cooling system and from direct contact with cooling material.
The product, which is usually a beverage, is thus cooled by means of vapour which passes from the evaporator to the absorber when the evaporator and absorber are connected such that a vapour path is formed by the connection. Cooling is thus achieved by natural convection due to the evaporator being at a lower temperature than the product. Where the evaporator includes water in the form of a water-based gel coating, for example, then a vacuum or a low pressure within the evaporator and absorber is required to ensure that evaporation occurs at relatively low temperature and to optimise the rate at which cooling occurs. Ideally, the rate of cooling is 30xc2x0 F. in a maximum of 3 minutes for 300 ml of beverage.
Preferably, either the desiccant region or the second region of the absorber unit comprises an absorber element having one or more pockets for the desiccant or heat sink material respectively.
In one embodiment, the absorber element is a metal container comprising one or more annuli such that these annuli form one or more desiccant pockets. One possible method of manufacturing the absorber and/or evaporator elements is by multiply redrawing metal. Preferably, the metal container and annuli thereof are surrounded by heat sink material.
In an alternative embodiment, the absorber element comprises one or more pouches, each divided into one or more pockets filled with heat sink material. Where a single pouch is used, it may comprise a corrugated strip of heat sealed foil or laminate of film and foil which may be coiled within the absorber unit in order to provide maximum cooling surface. In this embodiment, voids between the pockets may be filled with desiccant.
Usually, the absorber is connectable to the base of the can body. This connection preferably comprises a valve connected to the evaporator and a rupturable seal on the absorber unit such that the absorber unit plugs into the valve housing. Alternative connectors/actuation methods are described in copending patent application WO/GB00/02986 which is incorporated herein by reference.
According to a further aspect of the present invention, there is provided a method of cooling a beverage product in a can body, the method comprising: beading the upper end of a metal container and reverse redrawing said beaded container to form an evaporator element having an outer wall (34) formed from the upper end of the metal container and an inner wall (32) formed from the lower end of the metal container, said inner and outer walls being spaced by a gap; inserting the evaporator element into the can body and fixing the evaporator in the can body by clipping the curled edge (36) of the evaporator onto a ridge on the inside chine wall of the base of the can body to form a sealed unit which holds a high vacuum and is isolated from beverage product; fixing an absorber unit to the outside of the can body; evaporating liquid in the evaporator and providing a vapour path from the evaporator to a desiccant region of the absorber unit; absorbing moisture from the vapour by reaction between the desiccant and the vapour; and removing heat from the vapour and/or reaction of the desiccant, thereby cooling beverage product surrounding the evaporator.